1. Field of the Invention
The present invention relates to an information recording and reproducing apparatus which records information on an optical disc and reproduces the recorded information.
2. Description of Related Art
There is known an information recording and reproducing apparatus which records information on an optical disc, such as a DVD-R/RW, and reproduces the recorded information. On an information recording surface of the optical disc such as the DVD-R/RW, groove tracks serving as recording tracks and land tracks neighboring the groove tracks are formed. The land track has a function as a guide track for irradiating a light beam for recording or reproduction to the groove track. On the land track, prepits indicating pre-information including address information on the optical disc and the like are formed. Further, the groove track is wobbled at a frequency corresponding to a rated rotation speed of the optical disc. The prepits and the wobbled groove tracks are preformed before the shipment of the optical disc from a factory.
At the time of recording information, the information recording and reproducing apparatus of the optical disc such as the DVD-R/RW, detects a wobble signal indicating a wobble frequency of the above-mentioned groove track, and controls the rotation of the optical disc to be a predetermined speed based on the wobble signal. Also, the information recording and reproducing apparatus detects the prepits on the optical disc and obtains the pre-information. The information recording and reproducing apparatus sets optimum output of the light beam based on the pre-information, and obtains the address information on the optical disc from the pre-information to determine a recording position of the recording information on the optical disc, and then records the information.
The above-mentioned information recording and reproducing apparatus emits the light beam for recording and reproducing the information by an optical pickup, and receives a return light from the optical disc to output an electric signal. The wobble signal having the wobble frequency of the land track is generated from the electric signal outputted from the optical pickup, and a recording clock signal for recording the information is generated based on the wobble signal. More concretely, at the time of recording the information, a wobble signal level in a space portion of the recording signal is sampled by a sample-hold circuit, and the sampled level is held in a mark portion of the recording signal. Based on the output of the sample-hold circuit, the recording clock signal is generated. On the other hand, at the time of reproducing the information, the recording clock signal is generated based on the wobble signal without utilizing the sample-hold circuit.
Japanese Patent Application Laid-open under No. 11-345462 discloses a method that the recording clock signal is generated based on the wobble signal as explained above, and the information is recorded on the optical disc by utilizing the recording clock signal (it is also called “synchronized recording”).
However, if the sample-hold process is applied to the wobble signal detected from the optical disc in recording the information, phase delay occurs to the wobble signal after the sample-hold process due to an aperture. On the other hand, since the sample-hold process is not applied to the wobble signal in reproducing the information, the phase delay does not occur. Therefore, when the mode of the information recording and reproducing apparatus changes from an information reproducing mode to an information recording mode, a phase deviation occurs to the wobble signal which is a source of generating the recording clock signal. Variation of the frequency temporarily occurs to the generated recording clock signal due to the phase deviation, and the recording clock signal becomes unstable. Since information recording on the optical disc is performed in synchronism with the recording clock signal, accuracy of information recording on the optical disc decreases if the recording clock signal is unstable. As a result, problems such as deterioration of a reproducing error rate may occur in reproduction. Namely, at the time of changing the mode from the information reproducing mode to the information recording mode, the information recording temporarily becomes unstable, and the recording accuracy can decrease.